There are definitely pre-determined plans in the agenda of the James Webb telescope to take images from the universe, but if there is a need for any reason (intentional or emergency) to change the direction of the telescope to the other side of a subject in change the universe, is it possible to control this from ground stations and operators ?
And at what time ?

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    $\begingroup$ Sure there is, they have control software and hardware in NASA to do numerous things to the telescope, including reboot and update firmware (at least partially). So the answer is an obvious yes, but the time to turn JWST to new direction and stabilize afterwards should be out there somewhere. $\endgroup$
    – Vesper
    Nov 24, 2022 at 9:16
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    $\begingroup$ "change the direction of the telescope to the other side of a subject in change the universe" What does that mean? $\endgroup$
    – PM 2Ring
    Nov 24, 2022 at 12:08
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    $\begingroup$ "take images from the universe" is weird phrasing, and "to the other side of a subject in change the universe" is oddly broken English. I'm not certain if you just want to know if it can look at something else other than what it is currently looking at today (yes, it can move and change targets) or if it is free to look at anything we want it to (it cannot - it is highly constrained in its choice of orientation due to the fact that it must forever remain in the shadow of its own sunshield) $\endgroup$
    – Wyck
    Nov 24, 2022 at 18:40

1 Answer 1


The JWST is controlled from the ground. It is not locked in by a pre-programmed observing schedule.

Allocation of observing time on JWST is an ongoing process. “JWST observing programs may be modified or refined to better achieve approved science goals, or to accommodate changes in instrument performance“.https://jwst-docs.stsci.edu/jwst-opportunities-and-policies/jwst-general-science-policies/jwst-observing-program-modification-policy

Decisions around allocation of observing time on JWST include slew time (the time needed to move to a new target). Depending on the magnitude of the slew, it can take up to 20 minutes for the fluid in tanks to stop sloshing so the Fine Guidance System can acquire the new target. See this question on sloshing How are JWST tanks baffled to dampen slosh?

An additional “overhead cost” of acquiring a new target is acquisition of angular momentum in the reaction wheels. If the wheels become saturated, propellant must be expended to desaturate them. Observation programs can be designed to avoid this. https://jwst-docs.stsci.edu/jwst-opportunities-and-policies/jwst-general-science-policies/jwst-observing-overheads-and-time-accounting-policy


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